CS210834B1 - Method of producing pure isobuten - Google Patents

Abstract

The invention solves, obtaining or. isolation of isobutene from a mixture of hydrocarbons, especially with very close boiling points, especially from a mixture of butenes, isobutene, butadiene, butane and. isobutene with the aim of obtaining pure isobutene for further use in chemical syntheses, demanding on the purity of the isobutene used. According to this invention, pure isobutene is obtained from a mixture with hydrocarbons, especially from the hydrocarbon C^-fraction, in two stages. In the first stage, it is reacted with at least one aliphatic alcohol, preferably methanol and/or isobutanol, or their aqueous solutions, on a mixture of hydrocarbons, in which conjugated dienes may also be present, under increased pressure and the catalytic effect of acid catalysts. The selectively formed alkyl tert-butyl ethers and tert-butyl alcohol are isolated and in the second stage, under atmospheric or reduced pressure, are brought into acidic contact, whereby isobutene, aliphatic alcohol and water are formed. From the reaction mixture, high-purity isobutene is isolated in a known manner.

Description

1 210834

The present invention provides recovery of isobutene from mixtures of hydrocarbons, particularly with very close boiling points, especially mixtures of butenes, isobutene, butadiene, butane and isobutane.

The processes of isolation of isobutene from Cfraction by the action of sulfuric acid by conc. 40 to 65% by weight, most often conc. 65 Z, through the intermediate formation of tert -butylsulphuric acid and tert-butyl alcohol respectively, A. Fischer, Chem. Technology, Monoolefield, pp. 235-253. Akaderaie-Verlag Berlin (1957); Ariesi Nagaro: J. Jap. Petrol. Inst. 16.790 (1973); Schleppinghoff B .: Erdol und Kohle 2, 7, issue 5, 240 (1974)].

However, similarly as in the analogous isolation process, by reacting the aqueous hydrochloric acid solution to the C ^ciu fraction, tert-butyl alcohol and tert-butyl chloride are formed by the catalytic action of the metal chlorides with relatively high selectivity as intermediates. «: Hydrocarbon Process. 49, No. 2, Sec. 1, 1 37/1 970], which are easily separated from the hydrocarbon mixtures and dehydrochloride at 85 to 120 ° C and dehydrate under the regeneration of relatively pure isobutene, the disadvantage of which is the considerable corrosion of the apparatus and the higher build-up of products. I also have problems with acid recovery and waste disposal. Corrosion is also a problem with the selective esterification of acetic acid isobutene from the hydrocarbon fraction to form tert-butyl acetate, which in turn is easily decomposed by naisobutene and acetic acid at elevated temperature [jap. pat. 43-12562; J. Jap. Petrol. Inst. 16, No. 9, 790/19 7 3/3

Attention is drawn to the use of molecular sieves, where, for example, sewn with 5 X retains isobutene and isobutane molecules, but permits 1-butene and 2-butene molecules of other linear hydrocarbons / Jap. pat. 47-13251]. The molecular sutures with 8 to 8.2 R openings adsorb only isobutene, which is dimerized to diisobutenes / Jap. pat. 47-42803]. These procedures, similar to the other [I. I. et al. certč. USSR 407 864/1974 /], although interesting but challenging, energy and investment. However, the method of isolating isobutene from the hydrocarbon fraction, consisting in the selective hydration of isobutene with water at a temperature of 70-110 ° C and a pressure of 1.6-2.2 MPa under the catalytic effect of the ion exchange type catalyst, is interesting and striking. , for example, a modified polyethylene, polypropylene or polyvinyl chloride to form an aqueous solution of tert-butyl alcohol, which is dehydrated with a similar catalyst at 80-110 ° C, but also at a pressure of less than 0.3 MPa to form pure isobutene.

However, a disadvantage is the need for quota to improve the contact of isobutene with water to use polar solvents in the reaction medium in an amount of 10 to 70%, calculated on water or at least surface-active, especially non-ionic or cationic.

However, they do not solve the problem of isolation of isobutene from debris pyrolysis, respectively. incompletely butadieneized pyrolysis fractions, similar to any other interesting method (Verdol J.A.). No. 3,121,124, which solves the isolation of C4-C7-tert-monoolefins by precipitation with non-linear olefins by etherification with aliphatic alcohols and then regeneration of the tert-olefin by contact with a strong acid catalyst. The latter, in addition, only takes into account the chemical equilibrium between the alkyl-tert-butyl ether on the one hand and the isobutene with alcohol on the other.

The aforementioned and other drawbacks of the known isobutene isolation processes are solved and some of the last two methods are utilized and further improved by the present invention.

According to the invention, the process for obtaining pure isobutene from mixtures of monoolefins with diolefins and optionally paraffins at a temperature of 40 to 180 ° C and a total pressure of 0.1 to 5 MPa under the catalytic action of strong acids and / or acids is carried out as follows: that isobutene is isolated essentially from the carbonyl fraction - and / or the fraction containing from 2 to 50% by weight. % isobutene and containing 0.1 to 50 wt. of conjugated dienes such as 1,3-butadiene in the C, fraction, 4, 210834 of cyclopentadiene and piperylene in the fraction, by feeding at least one aliphatic alcohol and / or an aqueous solution of at least one aliphatic alcohol having carbon numbers of 1 to 5, preferably 1 to 5, 3, wherein at least one type of alkyl-tert-butyl ether and / or tert-butyl alcohol are separated from the unconverted hydrocarbons and are further catalytically dissolved in acidic contact, preferably on compounds of pentavalent phosphorus and / or sulphonated macromolecules and / or activated zeolites at a temperature of from 80 to 210 ° C, preferably from 100 to 160 ° C and a total pressure of from 0.05 to 0.4 MPa, preferably from 0.01 to 0.02 MPa, whereby pure isobutene is separated from the reaction product, optionally aliphatic alcohol and / or water, as well as unconverted alkyl-tert-butyl ethers and / or tert-butyl alcohol, which are preferably circulated. The advantage of the process for obtaining isobutene according to the invention is mainly the novel features of the possibility of isolating isobutene, e.g. from the low but also high butadiene pyrolysis fraction, without a more remarkable decrease in the content of this valuable diene. Further, the simultaneous function of lower aliphatic alcohols, both homogenizing and reactive.

The higher effect is mainly due to the distinctive differentiation of the total pressure at the selective synthesis of alkyl tert-butyl ethers and tert-butyl alcohol, which must be considerably higher than that of ethers and tert-butyl alcohol, resulting in high isobutene conversion and high conversion and selectivity of alkyl decomposition. tert-butyl ethers.

Finally, using isobutanol as the aliphatic alcohol, decomposition of the isobutyl tert-butyl ether formed, especially at temperatures above 120 ° C, from 1 mole yields 2 mole of isobutene. Another advantage is the flexibility of the process for obtaining isobutene not only from the starch potentially available aliphatic alcohols, but also when the isobutene excess is.

At that time, at least a portion of the honey of the zip product, i.e., the alkyl tert-butyl ether, e.g., methyl tert-butyl ether, can be consumed as an anti-knock component in motor gasoline. Said ether further, mainly with a higher number of carbons in the alkyl, such as solvents for coating agents, degreasers, alkylating agents and the like. Alkyl-tert-butyl ethers can also be easier to store than pure ones.

The potentially raw materials for obtaining pure isobutene are mainly the pyrolysis gases, in particular the pyrolysis of gasoline, in particular gas oil, so-called pyrolysis, or the pyrolysis fraction, the fraction from the products of the catalytic cracking of higher petroleum fractions, the isomerization isomers of isomerization of the equatorial alkenes , further products of disproportionation and dealkylation of hydrocarbons and the like. In the case of a pyrolysis fraction, for example, it may be a crude pyrolysis fraction, optionally refined from acetylene admixtures, or most often a substantially butadieneized pyrolysis fraction. Taking into account the type of starting material, in particular the content of 1,3-butadiene and 1,2-butadiene present, it is desirable to select the optimum type of selective addition catalyst alcohol isobutene. Thus, in the case of a high butadiene content in the starting hydrocarbon precipitate, the application of mainly sulfuric acid is suitable, less suitable is phosphoric acid and chlorofluoric acid. Also suitable are so-called ansol acids, such as sulfonated macromolecular substances, extra sulfonated isotactic polypropylene, sulfonated high density polyethylene with minimum melting index, especially sulfonated crosslinked high density and low density polyethylene, sulfonated polyvinyl chloride and especially sulfonated polyvinyl fluoride, sulfonated pyrolysis salts, high sulfonated crosslinked phenol formaldehyde resins, further highly sulfonated styrene- divinylbenzene resins, phosphorus pentoxide, phosphates, polyphosphoric acids polyphosphates themselves, but mainly on carriers, natural and synthetic zeolites, especially strong acid activated zeolites, polyheteroacids, as well as a combination of said catalysts. 3 210834

If sulfuric acid is used, there is no problem with catalyst life. In the case of amino acids, especially with the predominance of organic components, the catalyst can be "clogged" or the accessibility of -SO 2 H groups can be reduced, e.g. in the case of low-sulfonated phenol-formaldehyde or styrene-divinylbenzene resins by alkylation of their aromatic nuclei mainly isobutene and the like. In the isolation stage, it is suitable to operate at higher than atmospheric pressure, preferably at a pressure above 1 MPa, from the thermodynamic sources, which is usually achieved by the tension of other hydrocarbon components of the starting hydrocarbon feedstock, including nonconverted isobutene. and possibly other inert gas to favorably shift the chemical equilibrium, a higher total pressure than 3 MPa, as a rule no longer has a positive effect on the synthesis of alkyl-tert-butyl ether.

Both aliphatic saturated and unsaturated alcohols include methanol, n-propanol, 2-propanol, ethanol, allyl alcohol, n-butanol, isobutanol, sec-butanol, crotyl alcohol, as well as other higher aliphatic and cycloaliphatic alcohols such as cyclohexanol, methylcyclohexanol and the like, but also polyvalent aliphatic alcohols such as monoethylene glycol, diethylene glycol, triethylene glycol, glycerol, trimethylolpropane, neopentyl glycol and pentaerythritol. Further, aqueous solutions of said, especially lower aliphatic alcohols. Other similar catalyst catalysts may be used in the alkyl-tert-butyl ether decomposition step, as in the selective addition step, the difference being only in total pressure, with liquid acids being relatively unsuitable from a technological point of view.

In addition to alkyl-tert-butyl ethers and tert-butyl alcohol, diisobutenes can also be added to the decomposition, which also decompose at higher temperatures to form pure isobutene.

In contrast to the degree of synthesis of alkyl-tert-butyl ethers, the pressure at the stage of their decomposition should be low, usually as close as possible to atmospheric, but in no case higher than 0.4 MPa. Further details of the method of the invention as well as other advantages are apparent from the examples. Example 1

To a rotary autoclave (180 rpm) of stainless steel, we weigh 50 g of the sulfonated copolymer styrene-divinylbenzene resin / wet cation exchanger Ostion KS in H-form / with a total exchange capacity of 5.58 meq / g and 160 g aylalcohol. After closing the autoclave and removing air, 168 g of a mixture of isobutene with 4.5 wt. 1,3 butadiene. Thereafter, the autoclave content of the continuous rotation is heated to 80 ° C, reaching a pressure of 0.27 MPa, and maintained for 5 hours while the total pressure drops to 0.22 MPa.

Thereafter, the liquid product of this composition (in% by weight: 90.4 allyl-tert-butyl ether) is discharged from the autoclave via a condenser; 2,6 tert-butyl alcohol; 5.9 allyl alcohol and 0.9 diisobutenes. The liquid product is separated by rectification. The cation exchanger is used for a further experiment which, unlike the previous experiment, is carried out at 70 ° C for 9 h. Liquid product (312 g / contains / in% w / w: 94.3 allyl-tert-butyl ether); 1,3-tert-butyl alcohol; 0.3 diisobutene 3.2 unconverted allyl alcohol. The resulting .alpha.-tert-butyl ether from both experiments is then continuously injected into a 500 mm stainless steel reactor reactor with an internal diameter of 15 mm in which a center of 20 cm of a phosphate catalyst having a grain size of 1.25 to 3 mm containing 22.61 wt. . phosphorus in the form of phosphorus pentoxide on the support (pumice as carrier) and an acid number of 298 mg KOH / g. 3

There are 15 cm 3.5 mm diameter glass beads above the layer and below the catalyst layer, the whole reactor being heated to the desired temperature and the temperature controlled with an accuracy of 210834 4 to + 1 ° C. At reactor temperature / t. as both the catalyst itself and the glass beads / 150 ° C and the total pressure in the reactor 0.1 MPa is the injection of the allyl-tert-butylether ether 3 - 1 1.3 S <c1Dkat * h> The product is now marketed for the purification of pure isobutene.

The conversion of allyl-tert-butyl ether reaches 98 + 1 for isobutene selectivity of 99 + 0.3 Z. in a selectivity of up to 100 Z, they form diisobutenes; the liquid residue containing unconverted allyl-tert-butyl ether, diisobutenes and allyl alcohol is further divided, wherein allyl-tert-butyl ether with diisobutenes is again added to the allyl-tert-butyl ether and allyl alcohol feeds is conducted together with fresh and quenching cation exchange resin in the H-form catalyzed reaction with isobutene in a mixture with 1,3-butadiene. Example 2

Into the autoclave specified in Example 1, 42 g of cation exchanger were weighed in the H-form specified in Example 1, followed by 49.8 g of methanol and 200 g in a large proportion of the pyrolysis fraction of this composition. Of weight / 0.1 propane; 0.4 propene; 3.0 isobutane; 7.9 n-butane; 33,1 1-butene; 43.2 isobutene; 1,8 1,3-butadiene; 6.9 trans-2-butene; 3,5 cis-2-butene and 0.1 isopentane.

The autoclave is then heated to 80 [deg.] C. with constant rotation, the total pressure is increased to 3 MPa by pressing the tube and kept at this temperature for 2 Ir. Thereafter, the autoclave is cooled, the product removed, weighed, analyzed and divided. Methanol conversion of 99.2 + 0.2 is achieved with 99.9 Z selectivity for methyl tert-butyl ether. Conversion of isobutene reaches 98.7 Z, with a selectivity of 98.1 Z to methyl tert-butyl ether; 1.1 Z to tert-butyl alcohol and 0.8 Z to diisobutenes.

The thus obtained methyl tert-butyl ether containing 1 of tert-butyl alcohol and 0.6 of diisobutene is sprayed onto the phosphate contact, characterized in Example 1. Depending on the reaction temperature and the entrainment of the catalyst with methyl tert-butyl ether with tert-butyl admixture the alcohol and diisobutenes of the results depending on Table 1 are obtained from the reactive extracts of pure isobutene conditions in Table 1. as shown by the reaction Reaction temperature / ° c / load of catalyst Conversion of methyl tert-butyl-butyl ether alcohol Selectivity / 7 , lna isobutene for diisobutenes Dimethyl ether content in isobutene and non-naphthene / 7J 103 2, 7 54.9 100 98.4 1, 6 <0.1 108 2.4 61.8 100 98.6 1.4 < 0.1 112 1, 4 64.8 100 92.4 7.6 <0.1 124 3.0 94.2 100 97.5 2.5 <0.1 137 3.0 97.4 100 97.1 2.9 0.4 152 2.3 98.0 100 96, 1 3.9 0.6 Ex. 3 To 3 1 dm stainless steel autoclave equipped with jf480 propeller stirrer fig / min / s weigh 200 g of suro the fraction of the pyrolysis C. fraction of this 4 composition (v) by weight: propane = 0.61; propene of 0.24; isobutene = 2.00; n-butane - 10.20; 1-butene-18.35; isobutene = - 25.57; trans-2-butene = 4.60; cis-2-butene = 3.42; 1,3-butadiene = 34.26; methylacetylene z-0.39 aisopentane = 0.35. To this is added 75 g of methanol containing 2 g of sulfuric acid. The contents of the autoclave are heated rapidly to 85 ° C by means of a tempered jacket and the total pressure of the autoclave is brought to a value of 2.5 µg by supplying nitrogen. Thereafter, under continuous stirring, the temperature in the autoclave is maintained at 85 ± 1 ° C for 2 h, after which the autoclave contents are cooled to 18-20 ° C by means of cold water fed to the autoclave shell.

The contents of the autoclave are then discharged through a condenser and a gas separator, the nonconverted olefinefins, diolefins and paraffins being discharged from the separator through a condenser cooled to -30 ° C into a pressure cylinder and substantially nitrogen is degassed. The liquid phase after thorough separation of the gaseous hydrocarbons is freed of methanol by washing twice the amount of distilled water. The oily, water-insoluble layer is separated and 65.3 g of 99.8 Z of pure tert-butyl ether are obtained by rectification or extractive rectification.

This similar, as in Example 2, leads to phosphate contact to obtain pure isobutene and regenerate the tanol. Methanol from the decomposition of methyl tert-butyl ether as well as distilled from the aqueous etherification step solution is again fed to the synthesis of methyl tert-butyl ether. With this loss of 1,3-butadiene, only 1.8% rel. and n-butenes only 1.2% rel. Example 4

Methyl tert-butyl ether with a content of 13.5% methanol prepared essentially as described in Example 3, with the difference that the washing of methanol from the crude reaction product is carried out only with a partial amount of water and only a differential distillation from the oil layer. contact with high-acid synthetic type HY zeolite, this mechanical composition and / in% w / w:

Na O with 0.93; / NH 4 / ZO «10.07» CaO = 0.16; A12O3 ² 21.32; SiO2; 67.51; mol. SiO 2 / Al 2 O 3 ratio = 5.37.

A thick acidic zeolite of 50 cm @ 2 and in the form of rollers having a diameter of 3 mm and 6 mm is placed in the center of the glass reactor having an inner diameter of 30 mm and a length of 500 mm. Activation of the zeolite was carried out in an atomosphere of dry carbon dioxide by heating to 230 + 20 ° C for 2 h and then for 4 h at 600 + 50 ° C. Above activated. The layers of glass Rashig tubes are also present below and below the zeolite. 30 cm 3 above the zeolite and 20 cm below the zeolite.

The temperature of the catalytic bed of the high-acid activated type zeolite HY is maintained at a temperature of 160 ± 2 ° C, with methyl tert-butyl ether containing 13.5 wt. methanol is - 3 - 1> 0.8 8, crakat * k · The total reactor pressure is 101.2 KPa. Methyl 1-tert-butyl methacrylate conversion is 98.5%; isobutene selectivity 93.1% and diisobutene 6.9%. The isobutene formed contained 0.6 wt. dimethyl ether,

By raising the temperature of the catalyst bed to 190 ± 2 ° C under otherwise similar conditions, the conversion of methyl-tert-butyl ether 99.4% with the selectivity to isobutene 92.4 Z and the yield of 7.6 L is obtained. isobutene contains 2.9% by weight of isobutene; dimethyl ether, which is removed from the liquid screed, from either the outer or the outer surface, or to the surface.

The liquid fraction of the methyl tert-butyl ether decomposition products mainly contains methanol and isobutenes. Methanol after distillation is again carried out for the synthesis of methyl tert-butyl ether and non-converted methyl tert-butyl ether, usually with di-butyl ether, together with fresh methyl tert-butyl ether for decomposition. pressure of 0.1 to 0.15 MPa on zeolite. Example 5 v. , 3

To a 1 dm rotary autoclave specified in Example 1, 222 g of aliphatic alcohol, 13 g of wet cation exchanger in the H-form, also specified in Example 1 210834 6 and 2 g of sulfonated polypropylene powder were weighed and 172 g of biscuit was removed after removal of air with a content of 2.3 wt. 1,3-butadiene. Reaction conditions and results of addition of aliphatic C alcohols to isobutene. are shown in Table 2. 4 n-Butyl-tert-butyl ether / t is formed from n-butanol and isobutene. v. = 122.72 ° C (101.3 kPa), density at 20 ° C = 759.3 kg.cm and refractive index η = θ from 1.3962 / isobutanol isobutyl-tert-butyl ether / t. v. = 113.05 ° C / 101.3 kPa; density at 20 ° C = 749.9 kg.cm -1 and n30-1.3919 / s and sec-butyl-tert-butyl ether / t-butyl alcohol. v. = 114.57 ° C / 101.3 kPa; density at 20 ° C = 1.3952; n3 ° of 1.3952.

Isobutyl tert-butyl ether containing 3.2 wt. The tert-butyl alcohol is then fed to a phospholate cylindrical contact (3 x 5 mm / 50 cm 3) consisting of tetraphosphoric acid (HfiPv catalyst content of 17.1% w / w on bleaching earth). At a temperature of 147 + 2 ° C and a total pressure of 102 kPa, with a feed of 2.0 g / cm 2, "3, h" and nitrogen flow 3 11 te ac 5 cm • Cm cat, h 1e conversion, isobutyl tert -butylether 98.5 and tert-butyl alcohol 100 Z, whereby the selectivity of the formation of an extrudate / calculated theoretical formation of 2 moles of isobutene per mole of converted isobutyl tert-butyl ether (reaching 94 Z, selectivity to diisobutenes 4 7 »and higher hydrocarbons) 1.5X,

Table 2

Aliphatic Alcohol C4 Temperature / ° C / Reaction Time / h / Conversion Selectivity / Z / on Alcohol C4 isobutene alkyl-tert-butyl ethers tert-butyl alcohol diisobutene n-butyl alcohol 60 1 23,0 26,6 86.2 13.0 0.8 n-butyl alcohol 90 0.5 48, 1 51.9 93.8 3.6 2.1 n-butyl alcohol1 90 1, 5 72.2 74.5 93.1 3.5 3,4 isobutyl alcohol 90 0,5 45,4 48, 1 92,5 4,8 2, 7 isobutyl alcohol 90 1, 5 71,1 73,2 92,5 3,6 3,9 sec-butyl alcohol 88 0,5 14.6 18.2 68.9. 17,9 13,2 sec-butyl alcohol 90 1,5 22,0 33,1 66,6 11,8 21, 5 Example 6 v, 3 v. . z z

To a 1 dm rotary autoclave specified in Example 1, weigh 30 g of n-butanol, 30 g of isobutanol, 2 g of distilled water, 5 g of the cation exchanger specified in Example 1, dried in a vacuum oven at 3.95 kPa. and at 110 ° C for 4 h and 250 g of crude pyrolysis fraction characterized in Example 3. The autoclave content is heated rapidly to 85 ° C by means of a thermoformed mantle and the total pressure is adjusted to 4 MPa by supplying nitrogen.

With continuous stirring, the temperature in the autoclave is maintained at 85 t 1 ° C for 4 h. Conversion of n-butanol 9 8.3 Z, isobutanol 93.4 Z, water 99.8 7 and isobutene 97.1 70 is reached. on a pressure column, the reaction product is freed from unreacted C 1-6 hydrocarbons and the residue from the composition (v / w): 46.3 n-butyl alcohol, 44.0 isobutyl-tert-butyl ether, 7.3 tert-butyl alcohol, 1.8 isobutanol, 0.5 n-butanol and 0.1 hydrocarbons are fed to phosphate contact Specified in Example 5.

At 145 + 2 ° C, a total pressure of 102 kPa and a feed of 1.8 gm / m 2 / h 3 and a flow rate of 3 - 1 from a nitrogen of 4 cm, cm -1 at 4 is a conversion of n-butyl-tert-butyl ether 97.5 Z, isobutyl-tert-butyl ether 98.7 Z and tert-butyl alcohol 100 Z, wherein the selectivity of the formation of the debut / counted theoretical molar of 2 moles of isobutyl per mole of isobutyl tert-butyl ether (reaches 93.8 Z, selectivity of the extrudate 4, 4 Z and other 1.6 Z hydrocarbons.

Claims (2)

OBJECT OF THE INVENTION A process for obtaining pure isobutene from a mixture of monoolefins with diolefins and optionally paraffins at a temperature of 40 to 180 ° C and a total pressure of 0.1 to 5 MPa under the catalytic action of strong acids and / or anosylic acid, characterized in that isobutene is substantially isolated % of a hydrocarbon fraction of C 1 - and / or C 1 - fraction containing 2 to 50 wt. % isobutene and containing 0.1 to 50 wt. conjugated dienes such as 1,3-butadiene in the C 1 -fraction, cyclopentadiene and piperylene in the C 1 -fraction, by the action of at least one aliphatic alcohol and / or an aqueous solution of at least one aliphatic alcohol of 1 to 5 carbon atoms, preferably 1 to 3, wherein at least one type of alkyl tert-butyl ether and / or tert-butyl alcohol formed is separated from the unconverted hydrocarbons and further catalytically decomposes on an acidic contact, preferably on the PFA and / or sulfonated macromolecular compounds substances and / or activated zeolites at a temperature of 80 to 210 ° C, preferably 100 to 160 ° C and a total pressure of 0.05 to 0.4 MPa, preferably 0.01 to 0.1 MPa, wherein the reaction product is separated pure isobutene, optionally aliphatic alcohol and / or water, as well as unconverted alkyl tert-butyl ethers and / or tert-butyl alcohol, which are preferably recirculated. 2. A process for obtaining pure isobutene according to claim 1, characterized in that the mixture of monoolefins with diolefins and optionally paraffins is treated under the catalytic action of strong acids, preferably sulfuric acid and / or an inorganic, preferably sulfonated, organic macromolecules. containing -SOSOH groups in macromolecules, at least one aliphatic alcohol, preferably methanol and isobutanol, and / or an aqueous solution of an aliphatic alcohol, preferably an aqueous solution of methanol.